Apparatus of this kind is used particularly by haemophilia patients for measuring the coagulability of the blood, and hereby for the determination of whether there is need for the injection of a factor VIII preparation in order to avoid haemorrhages.
Equipment of this kind is known from EP publication no. 120 715. Here, the capillary element consists of a measuring cell in the form of an elongated channel at the end of a holder. Blood is sucked up into the channel, and the measuring cell can hereafter be inserted into a measuring apparatus with a light source and a photometer. The photometer measures the amount of light which, after the emission, passes the transparent side of the measuring cell, and which after reflection in the blood and the back of the measuring cell again passes through the transparent side.
This measuring cell does not, however, provide an accurate measurement result, the reason being that it is based on reflection. This gives rise to a measurement inaccuracy which is so great that it is unsuitable for the measurement of the coagulability of the blood. Furthermore, it is difficult to produce such a measuring cell, the reason being that the capillary element is built up of at least two parts which must be assembled for the formation of an element.
From the Swedish publication no. 404 260, an apparatus is known which can measure with greater accuracy, since this uses a beam of light and light detecting elements which are placed at an angle in relation to the light's direction of incidence in the sample.
However, this apparatus demands a precisely balanced positioning of these measuring means in relation to the blood sample, and in practice this means that the blood must be kept in a vessel-like container during the measurement. Since at a minimum there must be sufficient blood to cover the light detectors, a considerable amount of blood is required. This is a serious drawback for the user, the reason being that such a large amount of blood in practice can be obtained only with the help of a suction pump and hypodermic. Therefore, this apparatus is not suitable for so-called home use, where the user himself must be able to remove the blood sample necessary for a measurement.